So I have rented both lenses to test with my Canon C200
Initial observations.( im torn)

The 24-105 L lens has slightly faster auto focus and slightly better image stabilization although not a fair comparison as the 18-80 is heavier and this may be affecting results when comparing hand held.

The 18-80 has better image quality to my eye, seems sharper with a little more detail. The lens definitely adds a redish color bias. The ability to change Iris with smooth ring movement on the lens is great
also the servo zoom is nice. It is much heavier than the 24-105.

So in a nutshell
18-80
pros
-better image quality with more detail
- smooth servo
-nice manual ring control iris
- automatic iris
-wider and IMO more useful range
cons
-slightly slower auto focus
- more expensive
-much heavier for run and gun

Just wondering if anyone else has opinions or has compared these two lenses?
Is the autofocus slightly slower on the more expensive lens related to its larger size?

forgot to mention my rented version of 24-105 is the older model and the newer model is a little heavier
the other option is the 24-105 stm

Well you've summed up the main pros and cons of each lens.

I've had the 18-80mm for about 6 months now and have rarely taken it off my C300mk2. Autofocus seems very responsive and the lens is extremely sharp.

But the main draw of this lens for me is having a built in servo zoom. This adds an extra dimension to filming live action and a feature I've not had since starting to use large chip cameras using DSLR lenses about 7 years ago. The lens is also parfocal.

I'd like the lens to have a longer throw, say at least to 135, like the 18-135 STM lens I've been using previously. This entry level kit lens is extremely good value and very sharp, has a remote servo attachment option and is only one stop slower than the 18-80mm.

I'm sure you've probably seen the series of Lens reviews by Matt Porwoll for Abelcine but if not here's the link. In another video he also reviews the 24-105mm lens.

Behind the Lens: Canon Compact Servo 18-80mm | Tutorials & Guides | Blog & Knowledge | AbelCine
https://www.abelcine.com/articles/blog-and-knowledge/tutorials-and-guides/behind-the-lens-canon-compact-servo-18-80-mm

Does anyone know if the servo module that comes attached to teh lens (not the optional hand grip)
is removable? I have been renting the lens and controlling the servo from the camera joy stick. If teh servo unit can be removed can the servo still be controlled bytes camera? The reason I ask is one of teh controls on the servo is servo on servo off not sure if that function is mappable to the camera?

You forgot parfocal, one of the most important features for professional handheld shooting. The 18-80 is parfocal, the 24-105 is not. Personally, I have always disliked the 24-105, it has severe pincushion distortion, the sharpness is meh and I always felt it was overpriced for what it is. I have not tried the new version of the 24-105, I have read that it is only marginally better than the old one but I don't know that firsthand. Also, on a S35 imager, you will often regret having 24mm as your "wide", that is not a very wide FOV, the 18 is much more useful in my work. I also own the 18-135 STM IS F4.5-5.6 lens, the focal length is pretty much perfect. Sadly, the build quality is meh and because it is focus by wire, anytime you zoom from any length to any length, the image goes out of focus and refocuses, very quickly, but you still see it so there is this lag in the image following your zoom. This means you cannot get any usable snap zooms, stutter zooms, segmented manual zooms, which I like doing sometimes. This really means the 18-135 is only usable as a variable length prime, none of the zoom movement is the least bit usable although my clients have embarrassingly used my manual zooms with this lens, even on a prime time special I shot for Fox that aired in March, about shooting Prison Break in Morocco.

So as usual, there is no perfect lens. I have the 18-80 and the CN-E 70-200 T4.4 prototype on loan from Canon right now for an article I am writing. Both are great lenses but one wishes they were bit faster and for what they are, they are light but when compared to shooting with still lenses, both are hefty and make your Canon front-heavy unless you have a brick battery on the back to counterbalance. IMHO the ZSG-C10 is a must for either lens. The built in lens servo is not detachable, it is attached to the lens body via a ribbon cable. As far as focus speed, I am shooting a C200 with the lenses and you can set the focusing speed in the menu from really slow to very fast. So that is not a factor in my camera. I'll have to check if you can do the same on the C300 MKII, I have one here for another week or so. Which camera will you be using? I have a friend who just bought a C300 MKII and the 18-80. He shoots a lot of handheld and is very happy with the camera/lens combo. Your other accessory you should budget for is the 90 degree cable from Zacuto. If you don't, the stock cable will hit the table or surface you set your camera down on. Even the loaner lenses from Canon came with the Zacuto cables. Canon should just buy them and include them with the lens as the stock cable connection is a poor design.

I have the Canon C200,
The lens I rented came with the extra grip but I haven't been using it as you can also
control the servo with the handle grip that is attached to the camera.

I found my shots a little steadier using the 24-105 as the lower weight made for easier holding,
the one issue is the rented 24-105 is the older version and the newer version is a little bigger and heavier.

Like you said above there is no perfect lens

there is a bundle deal going on with the 18-80 where the lens is down to $4600 if you buy with the camera.

Do you think the 18-80 will hold its value?

The Canon 18-80 will hold it's value for far longer than the C200 which will be reduced by 10% to 20% within the next 6 months based on how Canon have dealt with the other cameras in the Cinema EOS range.

The Canon 18-80 will hold it's value for far longer than the C200 which will be reduced by 10% to 20% within the next 6 months based on how Canon have dealt with the other cameras in the Cinema EOS range.

The great thing is a lot of Sony FS7 owners, BMD and even Varicam LT owners are using the 18-80 so I agree with Mark, the 18-80 should hold value for a long time as the market for it is far beyond just Canon camera owners. Using still lenses to shoot video is a big compromise. Many of us do it but compared to a proper video lens, no comparison. Also, the built in lens servo on the 18-80 is not great, it's awkwardly placed for handheld shooting and there is very little nuance to speed versus the ZSG-C10. It's really just there because they had to give you a way to use the servo if you cheap out and don't buy the ZSG-C10.

I'm a little late on this but just wanted to say that in my experience the IS mechanism on the 24-105 is a bit too loud (audibly) for video use.

click-click-click-click

There is an STM version of the 24-105 but it's not an L series lens nor is it constant aperture.

In my opinion the 18-80 is the way to go. It's a perfect match for the C200.